Bird Flu Vaccine Takes Step Forward

WASHINGTON — Human tests show that an experimental vaccine stimulates the immune system to fight the bird flu strain that experts worry could spur a worldwide pandemic, a top government scientist said Saturday.

But the encouraging findings do not overcome the major hurdle: producing enough vaccine in the event of a pandemic, said Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases. The vaccine is grown in chicken eggs, and production can take months.

Fauci said early analysis of tests in healthy adults younger than 65 showed that the vaccine produced a strong immune response.

The test results, which were first reported by the New York Times, are "an important landmark in the broader plan of how you prepare a nation for pandemic flu," Fauci said.

But he added: "One of the sobering issues is, we still haven't solved the problem that we have had for years and years, which is vaccine production capability: Are we going to be able to make enough of this stuff?"

The H5N1 strain has killed about 50 people in Asia since 2003. Public health experts said the virus was mutating and could develop the ability to spread easily from person to person and kill millions.

Officials are working with vaccine makers to find ways to hasten vaccine manufacturing.